Steam generator for nuclear power plants, especially for pressurized water reactors

Abstract

Steam generator for nuclear power plants including a cylindrical housing, a tube bundle for conducting primary medium enclosed by the housing, at least one tube support plate holding the tube bundle, the cylindrical housing including a base member secured to the tube support plate and defining therewith inlet and outlet chambers for the primary medium, the cylindrical housing having a pair of opposing flanges on portions of the cylindrical housing located on opposite sides of the tube support plate, and flange connection means for tightly connecting the portions of the cylindrical housing on opposite sides of the tube support plate, the flange connection means being releasable for assembling and disassembling the tube bundle and including a stud bolt connection, the flanges having opposing sealing surfaces, a lip seal disposed between the sealing surfaces and having radially outwardly protruding lips tightly welded to one another, the lips having a radially inner region secured by respective circular bead welds to the flanges.

There is claimed: 
     
       1. Steam generator for nuclear power plants comprising a cylindrical housing, a tube bundle for conducting primary medium enclosed by said housing, at least one tube support plate holding said tube bundle, said cylindrical housing including a base member secured to said tube support plate and defining therewith inlet and outlet chambers for the primary medium, said cylindrical housing having a pair of opposing flanges on portions of said cylindrical housing located on opposite sides of said tube support plate, and flange connection means for tightly connecting said portions of said cylindrical housing on opposite sides of said tube support plate, said flange connection means being releasable for assembling and disassembling said tube bundle and comprising a stud bolt connection, said flanges having opposing sealing surfaces, a lip seal disposed between said sealing surfaces and having radially outwardly protruding lips tightly welded to one another, said lips having a radially inner region secured by respective circular bead welds to said flanges. 
     
     
       2. Steam generator according to claim 1 wherein one of said flanges is at said tube support plate, and the other of said flanges is on said base member, said base member being formed as a hemispherical housing base, and stud bolts extending through through-bores formed in said flange on said base member and having respective threaded bases threadedly secured in threaded bores formed in said tube support-plate flange, and respective threaded heads at the other ends thereof facing away from said tube support plate and protruding from said base-member flange, and tightening nuts threadedly secured on said threaded heads. 
     
     
       3. Steam generator according to claim 2 including primary-medium inlet and outlet unions connected at an inclination from below to said hemispherical base, said inlet and outlet unions having respective axes inclined to the longitudinal axis of said cylindrical housing to an extent that a ring zone wherein said base-member flange is disposed is located beyond an axial projection of said unions. 
     
     
       4. Steam generator according to claim 3 wherein said unions have, for a respective diameter and length, an inclination angle α with the longitudinal axis of said cylindrical housing which is smaller than 40°. 
     
     
       5. Steam generator according to claim 4 wherein said inclination angle is 30°. 
     
     
       6. Steam generator according to claim 1 including further flange connection means longitudinally spaced from said first-mentioned flange connection means and located in a region of the steam generator housing wherein said tube bundle is disposed, said further flange connection means also comprising a stud bolt connection. 
     
     
       7. Steam generator according to claim 1 wherein said tube bundle comprises a multiplicity of U-tubes, and the steam generator is a U-tube steam generator. 
     
     
       8. Steam generator according to claim 7 wherein said U-tube bundle has a cold leg, and including a preheating chamber in a region of said cold leg near said tube support plate, said further flange connection means being located above said preheating chamber. 
     
     
       9. Steam generator according to claim 1 wherein one of said flanges is at said tube support plate, and the other of said flanges is on said base member, said base member being formed as a hemispherical housing base, and stud bolts extending through through-bores formed in said flange on said base member and having respective threaded bases threadedly secured in threaded bores formed in said tube support-plate flange, and respective threaded heads at the other ends thereof facing away from said tube support plate and protruding from said base-member flange, and tightening nuts threadedly secured on said threaded heads, said tube support-plate flange being formed with additional bores coaxial with the threaded bores formed therein for affording access to a lifting tool for lifting said stub dolts, said threaded bases of said stud bolts being formed with a threaded blind bore for threadedly securing therein means for attaching said lifting tool to said stud bolts. 
     
     
       10. Steam generator according to claim 1 wherein said flange sealing surfaces have an austenitic plating, said lip seal being formed of austenitic material and having ring plating surfaces welded thereto and accessible from outside said housing. 
     
     
       11. Steam generator according to claim 1 wherein said lip seal comprises two mutually associated sealing rings, each having a semicircularly protruding lip, said lips having a mutually abutting joint and being weldable thereat to form a circumferential circular sealing bead.